1. Field of Invention:
The present invention relates to a control apparatus for an air conditioner which can be operated either with a room cooling operation mode or a room warming operation mode by comprising an IC logic circuit to control the sequence of compressor operation.
2. Prior Art:
The conventional defrosting control in room warming operation mode of an air conditioner has the following shortcomings. In the conventional defrosting control by a mechanical timer comprising a cam and a switch to be driven by a lever following the cam, a temperature detection of an evaporator is made during a short time period (for example 10 minutes) when the lever is falling into the detent part of the cam. The cam is so designed that the abovementioned detection is made with a specified time interval (for example, 1 hour). Then the air conditioner is set into the defrosting operation when the temperature is detected to be lower than a specified value. However, with such system, the detection can be made only for the specified short time period (namely only once for 10 minutes in 1 hour). Therefore, there might be a possibility of belated start of defrosting operation. There is another conventional defrosting system utilizing temperature difference between outdoor temperature and evaporator temperature. Though is very precise, this type of apparatus also has some problem of erroneous detection at the initial starting of the compressor or in a strong wind.
In general, the conventional air conditioners have utilized for room temperature control so-called hydraulic type thermostat which detects temperature change and turns on or off a compressor motor. In accordance with such system, due to a considerable hysteresis gap of temperature and rather slow response speed, a considerable temperature swing, which is larger than the temperature hysteresis gap of the thermostat, takes place in the room temperature. Therefore, the conditioned atmosphere is not satisfactorily comfortable. Especially when the atmosphere is wet and hot, due to effect of swing of moisture on top of that of the temperature, the conventional air conditioned room has not been satisfactorily comfortable. Let us elucidate a little more in detail. By operation of the compressor motor, the temperature and the moisture of the room air decreases. Then, at a detection of a specified lowered room temperature, the compressor is stopped by the function of the thermostat. Then, both the temperature and the moisture increase. Generally speaking, moisture reaches an unpleasant range faster than temperature's reaching an unpleasant range. However, the thermostat makes the compressor start by detection of only a temperature rise, and therefore, the air in the air-conditioned room becomes uncomfortably moist prior to a restoration of operation of the compressor. In order to avoid such inconvenience, there has been a need to provide a measure to restore the compressor motor prior to a detection of a specified temperature when a pausing of the compressor lasts longer than a specified period.
There is another important item in controlling the air conditioner to prevent undesirable locking of compressor which is likely to occur when the compressor is operated to restore immediately after a stopping thereof. Namely, immediately after a stopping the compressor has a very high back-pressure. Therefore, if a compressor motor is energized immediately after a stopping, such high back-pressure hinders the rotation of the motor thereby causing a harmful overloading sometimes leading to a burning of the compressor motor. In order to avoid such inconvenience, there has been a need to provide a mean to prevent a restoration of operation of the compressor immediately after a stopping.